PROJECT SUMMARY Although there is a growing body of research suggesting that social media promotion of non-cigarette tobacco products is rapidly growing,1-3 digital marketing remains to be an understudied domain in tobacco control. Social media messages marketing tobacco products are currently unregulated, target youth and vulnerable populations, often contain misinformation, feature branded merchandise and celebrity or ?influencer? promotion. Youth use social media at higher rates than the general population in the U.S.,4, 5 which potentially multiplies the effect of social media marketing. The existing regulatory imbalances in treatment of non-cigarette products and digital marketing may explain persistent disparities in tobacco use and in marketing exposure among U.S. population subgroups.6-8 In particular, while cigarette smoking prevalence continues its decades-long decline, disparities in consumption of smokeless tobacco (ST) are striking, with 8.4% of high school males reporting ST use in 2018.9- 11 Thus, the use of flavored and pouched ST products that are predominantly used by novices and youth is on the rise. Furthermore, public misperceptions exist about the relative risk of lower harm products such as ST and e-cigarettes and social media messages about these products often feature misleading information regarding health risks. Understanding the impact of exposure to this content can provide meaningful insights for tobacco control as social media data can serve as valuable measures of population norms, targeted marketing, and other previously unmeasured contextual factors associated with health outcomes. Unfortunately, to date, no studies have examined the population level impact of social media marketing of smokeless tobacco. This project will advance the scientific knowledge on smokeless products by filling this critical research gap. The overarching goal of this project is to examine the effects of exposure to ST-related social media content and provide timely scientific basis for potential regulatory actions on restricting marketing for these products. The specific aims of the proposed project are: to identify and characterize potentially regulatable social media message content related to smokeless tobacco by source, major themes (e.g., new user targeting, health risks, flavors)(Aim 1); to examine the impact of smokeless tobacco social media content exposure on ST use, attitudes towards ST, harm perceptions, perceived prevalence of use, initiation, and intentions to use ST (Aim 2); to study whether/to what extent tobacco control policies modify the impact of exposure to social media content (Aim 3). These aims will be accomplished by applying innovative research and analytic methods to a unique combination of data sets, including social media data from Twitter, Instagram and Facebook and survey data on tobacco-related outcomes. Findings will provide highly policy-relevant scientific evidence on the impact of social media marketing of ST products. This project holds the potential to provide unique insight into the influence of digital ST promotion on individual attitudes, beliefs, and behaviors and will build a scientific and methodological base for surveillance and potential regulation of commercial advertising messages on social media platforms.